Among many other things, “The Dark Knight” proves that Batman doesn’t need a Robin. But he does need a Joker.

This intense and haunting sequel to 2005’s “Batman Begins” is an example of pulp material done right. It doesn’t stint on the requirements of a summer blockbuster (chase scenes, fancy gadgets, breathtaking plunges from tall buildings), yet it creates an aura of true mystery around itself. And it even seems to catch the current civic mood — disenchantment, frustration and helplessness are its primary topics.

If this sounds a little angst-heavy, you got it. Gotham City is terrorized by a relentless scourge, the Joker (Heath Ledger), a cackling psycho with a purely nihilistic attitude toward crime. “Some men just want to watch the world burn,” someone says, and that’s our boy Joker.

Batman is there to provide vigilante justice. This is the alter ego of billionaire Bruce Wayne (Christian Bale), and he has a new suit and new wheels in this one.

District Attorney Harvey Dent (Aaron Eckhart) seems committed to stopping corruption in Gotham, and he’s convinced Bruce’s ex, Rachel (Maggie Gyllenhaal), of his sincerity. In more ways than one.

Several returning cast members play important supporting roles, especially Gary Oldman, and Michael Caine and Morgan Freeman are back as Bruce Wayne’s key assistants. But while Aaron Eckhart is very strong as the crusading Dent, the movie is owned by its villain.

Heath Ledger had completed his role as the Joker before his untimely death in January. His performance is scary and funny, if not quite as original as some of Ledger’s other work. The Joker wears bad pancake make-up and greasy greenish hair, and his voice drops unpredictably into menace or mockery, depending on the moment.

Ledger makes it really memorable by embodying a certain philosophy, a pranksterish approach to creating chaos. He’s a classic villain, and the next “Batman” movie won’t be the same without him.

Director Christopher Nolan returns to the helm, and he’s stirred just the right number of stimulating ideas into the comic-book universe. He’s also got a wild eye for loaded imagery: There’s a shot of the Joker striding away from a hospital that will peel a layer off your eyeballs.

“The Dark Knight” isn’t the slightest bit light-hearted, and its conclusion contains some sinister suggestions that will have to be dealt with in a third installment. Good. It can’t come a minute too soon.